Atmospheric inorganic nitrogen in marine aerosol and precipitation and its deposition to the North and South Pacific Oceans

Abstract

Aerosol and rain samples were collected between 48°N and 55°S during the KH-08-2 and MR08-06 cruises conducted over the North and South Pacific Ocean in 2008 and, to estimate dry and wet deposition fluxes of atmospheric inorganic nitrogen (N). Inorganic N in aerosols was composed of~68% NH 4 + and~32% NO 3 -(median values for all data), with~81% and~45% of each species being present on fine mode aerosol, respectively. Concentrations of NH 4 + and NO 3 − in rainwater ranged from 1.7-55 μmol L −1 and 0.16-18 μmol L −1 , respectively, accounting for~87% by NH 4 + and~13% by NO 3 − of total inorganic N (median values for all data). A significant correlation (r00.74, p<0.05, n010) between NH 4 + and methanesulfonic acid (MSA) was found in rainwater samples collected over the South Pacific, whereas no significant correlations were found between NH 4 + and MSA in rainwater collected over the subarctic (r0 0.42, p>0.1, n06) and subtropical (r00.33, p>0.5, n06) western North Pacific, suggesting that emissions of ammonia (NH 3 ) by marine biological activity from the ocean could become a significant source of NH 4 + over the South Pacific. While NO 3 − was the dominant inorganic N species in dry deposition, inorganic N supplied to surface waters by wet deposition was predominantly by NH 4 + (42-99% of the wet deposition fluxes for total inorganic N). We estimated mean total (dry+wet) deposition fluxes of atmospheric total inorganic N in the Pacific Ocean to be 32-64 μmol m −2 d −1 , with 66-99% of this by wet deposition, indicating that wet deposition plays a more important role in the supply of atmospheric inorganic N than dry deposition.

Western Pacific atmospheric nutrient deposition fluxes, their impact on surface ocean productivity

“…Our results are consistent for this region with those from sampling on island stations in the NW Pacific such as Chichi‐jima [ Matsumoto et al ., ]. In our data, and in the other for this region [ Jung et al ., ], aerosol ammonium concentrations are higher than nitrate. Liu et al .…”

“…The nitrate and ammonium concentrations we report here are consistent with other data from the western Pacific and generally higher than those seen farther east (i.e., east of 160°E) in the Pacific [ Jung et al ., ]. This lateral gradient is consistent with dilution and deposition of terrestrial‐origin aerosol during eastward transport and is also evident in model estimates [e.g., Duce et al ., ].…”

“…The concentrations we report here for the air masses crossing zone A are higher than those reported by Jung et al . [] probably reflecting differences in the magnitude of the impact of industrial emissions from Asian sources on samples of air masses with somewhat different trajectories over that region. Our results are consistent for this region with those from sampling on island stations in the NW Pacific such as Chichi‐jima [ Matsumoto et al ., ].…”

“…There have been numerous studies of atmospheric aerosol concentrations over the Pacific Ocean, particularly the North Pacific, including studies of dust and iron transport [ Uematsu et al ., ; Matsumoto et al ., ; Moffet et al ., , Prospero et al , , Wagener et al ., ], nitrogen [ Savoie et al ., ; Jung et al ., ; Nakamura et al ., ; Miyazaki et al ., ; Miyazaki et al ., ; Zhang et al ., ; Ooki et al ., ], as well as contaminants [ Uematsu et al ., ; Moffet et al ., ] but fewer studies of phosphorus [ Furutani et al ., ; Hsu et al ., ]. Together, these studies emphasize the general patterns of atmospheric transport over the Pacific (discussed further below) with high concentrations of dust (and associated iron), anthropogenically derived metals and nitrogen in the Asian plume passing over the NW Pacific, particularly in spring.…”

Estimation of sulfur, fluorine, chlorine and bromine fluxes at Mid Ocean Ridges using a new experimental crushing and extraction method

“…After that, we converted all the sulfur compounds to sulfate ions by adding 1-2 cm 3 of hydrogen peroxide (30%) into the filtered solution using the same method for volcanic gas analysis (Giggenbach, 1975). Then S, F, Cl and Br concentrations in the solution were measured using an ion chromatography (IC; Dionex-320, Thermo Scientific Dionex) with a standard procedure (Jung et al, 2011). The anions (F -, Cl -, Br -, NO 3 -and SO 4 2-) were analyzed using an AS17 anion exchange column with an AG17 guard column (Thermo Scientific Dionex).…”